You’re cool and environmentally conscious. You eat organic and live green, right down to your trendy hemp shoes. You probably even drive a Prius and subscribe to Mother Jones.

But if you live in a city of much size, to be deeply green you must pimp your ride with a folding bike.

Europeans have been making and riding folding bikes for years. Asia, long a bicycle-dominant part of the world, has found folding bikes ideal for their cities’ crowded streets.

Now America is gaining speed and folding-bike sales are growing.

A folding bike can be pricey (some models cost well above $2,000), but you can also find one for less than $300. Increasingly they can be brought aboard buses, subways and trains, folded so small they slip into carrying bags and cause no crowding complaints. The battle of squeezing a bike into elevators, apartments and offices becomes moot when your cycle can collapse to less than 3 feet in height. (Check with airlines before assuming you can fly your bike-in-a-bag as luggage.)

The collapsible cycle’s origins are debated — some say it was invented by an American in the 1890s, others credit the French military, according to The Folding Cyclist. The folding cycles were widely used by the military in Europe during both world wars.

In the 1980s, two brands of folding bikes were born — Andrew Ritchie’s Bromptons and Dr. David Hon’s Dahons. Today, both are still big wheels in the folding bike field. Dahon is the largest, and one source says the company sold 638,000 bikes from 2006 to 2007. Bromptons are very popular in the UK and Asia.

Issues to consider before buying: How long does it take to fold and unfold? How much does it weigh? What size are the wheels?

Look at performance, speed and stability, and make sure the bike fits you.

How and where you’ll use the bike is essential to your decision. Will you be on park paths during vacations, or traversing the mean streets of the big city getting to work? Will you ride long distances or lug your bike around as much as you ride it?

Folding bikes look a little odd, which is likely part of the appeal. Some of the colorful bikes – especially when folded — look more like works of industrial art than modes of transportation.

Many have elongated posts for seats and handlebars. The wheels can be very small (8- to 12-inch) but stability is sacrificed at that size. Most folding bikes have wheels in the 16- to 18-inch range (although some come as large as 26 inches). The small wheels can make the ride a bit rougher but the bikes are lighter and fold faster. The lightest weigh about 22 to 25 pounds. Most bikers prefer those with multiple gears rather than single-speed, and those with internal gears in the hub mean no more grease on your pants.

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